An uplink control channel (PUCCH, physical uplink control channel) is used to carry ACK/NACK (acknowledgement/negative acknowledgement) feedback for a downlink data channel (PDSCH), such as PUCCH format 1/1a/1b, and may also be used to carry channel status information (CSI) of a downlink channel, such as PUCCH format 1/2a/2b. In Rel. 10, an uplink control channel PUCCH takes a CAZAC (const amplitude zero auto-correlation) sequence as a basic sequence, which is divided into 30 sequence groups, an index of which being denoted by u, uε{0, 1, 2, . . . , 29}; each sequence group contains one or two basis sequences, and v denotes an index of a basic sequence in a sequence group, v=0, 1. A PUCCH basic sequence of a user is decided by a sequence group index u and a basic sequence index v in a sequence group. All users in the same cell employ identical sequence groups, and users in different cells employ different sequence groups. As different users in a cell employ identical sequence group indices, when two users occupy identical uplink physical resource blocks (PRBs) to transmit PUCCHs, orthogonality of PUCCHs in the cell may be ensured by different cyclic shifts (CSs) and/or different orthogonal cover codes (OCCs), so as to ensure relatively low inter-cell interference. And at the same time, multiple users may occupy identical CSs and/or OCCs, but occupy different PRBs, so as to ensure their orthogonality. A physical resource nPUCCH1 occupied by a PUCCH corresponds to a combination of a CS, an OCC and a PRB. For dynamic PDSCH transmission, the physical resource nPUCCH1 of the PUCCH format 1/1a/1b is dynamically decided by a index of a CCE (control channel element) of a PDCCH (physical downlink control channel) scheduling the PDSCH, nPUCCH1=nCCE+NPUCCH(1); where, nCCE is an initial index of the CCE of the PDCCH, and NPUCCH(1) is a cell common parameter, which is configured via high-layer signaling.
As evolution of a EUTRA (evolved universal terrestrial radio access) network, many new scenarios appear, such as a heterogeneous network having identical or different cell ID. New features of data channel and control channel need to be introduced. And for an enhanced PDCCH, following content needs to be taken into account:
being capable of supporting an increased control channel capacity;
being capable of supporting an ICIC (inter-cell interference coordination) technology in a frequency domain;
being capable of increasing spatial reutilization of a control channel resource;
being capable of supporting beamforming and/or diversity;
being capable of operating in a new carrier type and a MBSFN (multicast broadcast single frequency network) subframe; and
being capable of coexisting with conventional UE (user equipment) in the same carrier.
Expected features include having an ability to schedule frequency selection and reduce inter-cell interference. Based on the above demand, an E-PDCCH (enhanced PDCCH) may be in a conventional PDSCH (physical downlink shared channel) area, and frequency division multiplexed with the PDSCH, that is, for at least one user, an E-PDCCH and a PDSCH occupy different physical resource block pairs (PRB pairs), as shown in FIG. 1. In order to improve spectral utilization of an E-PDCCH, a single PRB may carry E-PDCCHs of multiple users. An E-PDCCH has two mapping schemes, that is, localized mapping and distributed mapping, as shown in FIG. 2. For the localized mapping, it is expected to obtain a frequency selection scheduling gain and a frequency selection beamforming gain, i.e. an eNB is capable of transmitting E-PDCCHs in a subcarrier having a relatively good channel response. And for the distributed mapping, it is expected to obtain a frequency diversity gain.
Similar to ACK/NACK feedback of a PDSCH scheduled by a PDCCH, ACK/NACK feedback of a PDSCH scheduled by an E-PDCCH may still be carried by a PUCCH. A physical resource of the PUCCH may be dynamically implicitly decided by parameters including at least NPUCCH(1) and an index of an E-CCE of an E-PDCCH, etc. However, following problems may exist in deduction of the physical resource of the PUCCH:
1) the E-PDCCH has two mapping schemes, the localized mapping and the distributed mapping, the indices of their E-CCEs may be independent; while the PDCCH has only one mapping scheme, and the indices of its CCEs is unified for all the users. Assuming that the PDCCH occupies former three OFDM symbols, a total number of corresponding CCEs is 20, PDCCHs of different users occupy different CCE of these 20 CCEs, for example, a user 1 and a user 2 occupy logically neighboring CCEs, the user 1 occupying #11 CCE, and the user 2 occupying #12 CCE, then PUCCH resources nPUCCH(1) of these two users are different, which are nPUCCH1=11+NPUCCH(1) and nPUCCH1=12+NPUCCH(1), respectively. While for an E-PDCCH, if the user 1 employs the distributed mapping and the user 2 employs the localized mapping, and the user 1 and the user 2respectively occupy a #1 CCE in a search space of the distributed mapping and a #1 CCE in a search space of the localized mapping, then the PUCCH resources nPUCCH(1) of these two users are identical, which are both nPUCCH1=1+NPUCCH(1), that is, collision of PUCCH resources occurs. Hence, the problem of resource collision in different mapping manners needs to be solved for PUCCH resources to which an E-PDCCH corresponds;
2) in the same mapping manner, resource collision may possibly occur in the PUCCH resources to which an E-PDCCH corresponds. For example, in the localized mapping manner, a search space of each user is independently configured, and the indices of its E-CCEs are also calculated in respective search spaces of the users. Therefore, when E-PDCCHs of two users respectively occupy resources of identical CCE indices in respective search spaces, such as both of them occupy a #1 CCE in the search space of themselves, then the resources nPUCCH(1) of the two users are identical, which are both nPUCCH1=1+NPUCCH(1), that is, collision of PUCCH resources occurs. In order to solve such a problem, introduction of a PRB index may be taken into account to implicitly calculate PUCCH resources; and
3) for the localized mapping manner, in order to obtain the frequency selection scheduling gain, the eNB will transmit E-PDCCHs at best bands of a user. Since best bands of different users are often not neighboring to each other, it is possible that a difference between indices of PRBs mapped by E-PDCCHs of different users may be very large; for example, if E-PDCCH of the user 1 is mapping into a first PRB and E-PDCCH of the user 2 is mapping into a 37th PRB, then PUCCH resources to which the two users correspond may be different PRBs. In an existing PUCCH structure, one PRB may carry 3X PUCCHs, where, X is the maximum number of CSs that can be supported in one PRB. Even though the scheduled users at a certain moment are only the 2 users, resources reserved by a PUCCH are also at least 2 PRBs, which results in that the spectral utilization of the PUCCH is very low. Such a problem is relatively less severe in a PDCCH. As the total overhead of PDCCHs of all users in a cell at a certain moment may be dynamically indicated by a PCFICH (physical control format indicator channel) (taking an OFDM (orthogonal frequency division multiplexing) symbol as a minimum unit), although it cannot be corrected to a CCE, a dynamic range of a CCE is effectively limited, thereby avoiding the above problem of waste of E-PDCCHs.
It should be noted that the above description of the background is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present invention.